Several techniques are employed in clinical practice for breaking abnormal concretions appearing in the biliary and/or urinary system of a human body into pieces for further removal of the pieces from the body. The term “concretion” as used herein refers to solid calculous formations of urates, oxalates and phosphates, e.g. gallstones, kidney stones, cystine stones and other calculi, lodged in the ducts and cavities of a living body. Although procedures have varied, most of them have involved dilatating, anesthetizing and lubricating the urinary or biliary tract, and then attempting to grasp the calculus for crushing it, and then dragging it out.
For example, extra- and intra-corporeal shock wave lithotripsy is widely used which employs high-energy shock waves to fragment and disintegrate calculi. In extracorporeal shock-wave lithotripsy, an energy needed for stone fragmentation, in the form of shock waves, is transferred from an outside source through body tissue to the calculi. In turn, intra-corporeal shock wave lithotripsy utilizes a probe advanced with the aim of an endoscope and positioned in proximity to the calculus. The shock waves, required for fragmentation, are transferred through the probe to the calculus, and the treatment process can be visualized during fragmentation.
Ultrasonic lithotripsy technique is known that utilizes an ultrasound probe emitting high-frequency ultrasonic energy towards a concretion. For this technique, direct contact of the probe tip and stone is essential for effectiveness of ultrasonic lithotripsy.
Lasers are known as an alternative source of energy in lithotripsy, especially for the destruction of renal and biliary stones. Various types of laser lithotripsy probes with a variety of laser sources, including pulsed dye laser, alexandrite laser, neodymium laser, holmium laser and other lasers, have been developed.
Electrohydraulic lithotripsy (EHL) has been an accepted form of therapy for the destruction of urinary stones both in the human bladder and within the individual ureters. EHL is extremely effective in breaking large urinary stones into pieces small enough for basket extraction or simple passage. When EHL is selected to affect the destruction of the stone, the EHL probe is placed in proximity to the stone. By means of an electrical discharge, a shock wave is produced which impacts the surface of the stone and produces tiny cracks. When enough cracks have been made, the stone shatters into small pieces. The individual pieces can then be attacked one at a time, or they can further be removed by basket extraction.
A lithotripsy technique of electro-impulse destruction of materials is also known in the art (see, for example, U.S. Pat. No. 7,087,061 to Chernenko, et al). Contrary to electrohydraulic destruction, employing electrodes which are not in direct contact with the object, electro-impulse destruction utilizes a probe with electrodes which are placed directly on the object's surface. This technique is based on the Vorob'evs effect that provides certain features of the discharge observed when a solid dielectric in contact with two rodlike electrodes is placed in a liquid dielectric medium, and a voltage pulse with increasing front is applied to the electrodes. According to this effect, when the pulse front slope is small (e.g., the pulse rise time is more than about 0.5 microseconds), the discharge develops in the surrounding liquid over the solid dielectric surface rather than penetrating into the solid body. On the other hand, in the case of a sufficiently large slope of the pulse front, the discharge propagates through the solid and produces its fracture with cleavage of the surface fragments (see, for example, G. A. Masyats, Technical Physics Letters, Vol. 31, No. 12, 2005, pp. 1061-1064. Translated from Russian from Pis'ma v Zhurnal Tekhnicheskoi Fiziki, Vol. 31, No. 24, 2005, pp. 51-59).
A problem associated with lithotripsy probes is that the calculi are not captured during treatment. For example, a stone can be pushed along the ureter towards the kidney in response to efforts to treat it. Likewise, the stone can also move to the side of the catheter and wedge between the ureter wall and the catheter.
There are known medical devices combining a lithotripsy probe used to break calculi with a retrieval collapsible wire basket that allows a secure hold on a urinary or biliary stone, while the destructive forces of the lithotripsy probe are used to shatter the stone. One of the advantages of such combined lithotripsy devices is in the fact that the operator using such a device is not required to change a lithotripsy probe and a retrieval basket in the middle of the procedure, within the very restrictive confines of the urinary or biliary tract.
For example, U.S. Pat. No. 5,176,688 to Narayan, et al. describes a stone extractor and method in which a stone is captured in a retrieval basket at the distal end of an elongated tubular member and broken into pieces while it is held by the basket. The stone is broken up by a reciprocating shaft which extends through the tubular member into the basket and is driven toward the stone by a spring to provide an effective hammering action without injuring the surrounding tissue. The stone is removed from the body by withdrawing the tubular member from the body with the pieces of the stone in the basket.
U.S. Pat. No. 5,397,320 to Mitchell, et al. describes a laparoscopic surgical device which comprises an elongated shaft having a plurality of electrically conductive flexible ribs connected to the distal end of the shaft and to one another to form a cage or basket. Upon placement of an organic body in the cage, the ribs are electrically energized. The organic body is pressed against the ribs to dissect the ribs in a single cauterization operation.
U.S. Pat. No. 6,319,261 to Bowers describes a combination lithotripsy device for the destruction of calculi such as urinary stones in the human bladder, individual urinary ureters, the biliary tract, or other locations in the human body. More specifically, the device includes an electrohydraulic probe combined with a basket which consists of multiple electrical conduit wires that act both as electrical conduits and collectively act as a grasping device.